Java Database Connectivity (JDBC)

When I try to retrieve a value from a simple select in a SQL

I get the following ugly error:

java.lang.ArrayIndexOutOfBoundsException
at oracle.sql.LnxLibThin.lnxnuc(LnxLibThin.java:6070)
at oracle.sql.NUMBER.toText(NUMBER.java:2664)
at oracle.jdbc.driver.OracleStatement.getStringValue(OracleStatement.java:3531)
at oracle.jdbc.driver.OracleResultSetImpl.getString(OracleResultSetImpl.java:434)


The exception is thrown in point ticked below

while (rs.next())
{

for (int i=1; i<=numberOfColumns; i++) {

// here the exception is THROWN in the first row of Resultset
myvar = "" + rs.getString(i);


}


}


The SQL works in PL/SQL bringing the following resultset:

0,0
2,0
2,0
1,5
0,0



Do u have any idea?
Thanks.

C.